Fixing apparatus and image forming apparatus including the same

Abstract

A fixing apparatus and an image forming apparatus of the present invention are arranged so that a fixing control section causes a fixing roller to additionally rotate so that the additional rotation corresponds to a driving delay time also after turning OFF an external heating roller heater when shifting from a temperature raising step in which surface temperature of the fixing roller is raised so as to be equal to a preset fixing temperature to a standby mode and when turning OFF the external heating roller heater and stopping the fixing roller. As a result, it is possible to provide a fixing apparatus and an image forming apparatus in which a surface of a fixing roller is free from deterioration or breakage caused by local heating carried out by an external heating roller.

1. A fixing apparatus, comprising: a fixing member which is rotatable; a pressure member for pressing the fixing member; and an external heating member for coming into contact with a surface of the fixing member so as to heat the surface from outside, a recording material being allowed to pass through a space between the fixing member and the pressure member so as to fix a toner image formed on the recording material,
 said fixing apparatus comprising a control section for controlling a state in which the fixing member is driven and for controlling a state in which power is supplied to heat sources respectively provided in the fixing member and the external heating member, wherein 
 the control section carries out a first fixing member maintenance process, in which the fixing member is kept rotating also after stopping supplying power to the heat source of the external heating member, when shifting from a temperature raising step for raising a surface temperature of the fixing member so that the surface temperature is equal to a preset fixing temperature to a standby mode so as to stop supplying power to the heat source of the external heating member, and 
 based on a surface temperature of the external heating member, the control section keeps the fixing member rotating during a period in which a surface temperature of the external heating member drops in a contact portion with respect to the fixing member so as to be equal to or lower than a durable temperature of the surface of the fixing member; and 
 the control section carries out a second fixing member maintenance process, in which time for beginning to supply power to the heat source of the external heating member is delayed from a time for beginning to supply power to the heat source of the fixing member, when carrying out a temperature raising step on start up or a temperature raising step upon restoration from a sleep mode; 
 wherein the control section begins to supply power to the heat source of the external heating member when the surface temperature of the fixing member attains a softening temperature of toner, in carrying out a temperature raising step on start up or a temperature raising step upon restoration from a second sleep mode in which the surface temperature of the fixing member rises from a temperature lower than the softening temperature of the toner, and after the toner softening temperature is reached both the heat source in the fixing member and the heat source in the external heating member are turned on until a fixing temperature is reached. 
 
   
   
     2. The fixing apparatus as set forth in  claim 1 , wherein the control section carries out the first fixing member maintenance process when finishing a temperature raising step on start up. 
   
   
     3. The fixing apparatus as set forth in  claim 1 , wherein the control section carries out the first fixing member maintenance process when finishing a temperature raising step upon finishing a printing process. 
   
   
     4. The fixing apparatus as set forth in  claim 1 , wherein the control section keeps the fixing member rotating during a period in which a surface temperature of the external heating member drops in a contact portion with respect to the fixing member so as to be equal to or lower than the preset fixing temperature. 
   
   
     5. The fixing apparatus as set forth in  claim 4 , wherein the control section begins to supply power to the heat source of the external heating member at a timing, at which a leading end of a first fed recording material reaches the space between the fixing member and the pressure member, when carrying out a temperature raising step upon restoration from a first sleep mode in which step the surface temperature of the fixing member rises from a temperature higher than a softening temperature of toner and lower than the preset fixing temperature. 
   
   
     6. The fixing apparatus as set forth in  claim 1 , wherein in the temperature raising step on start up, the control section carries out a thermal storage process, in which supply of power to the heat source of the external heating member is controlled in synchronization with supply of power to the heat source of the fixing member, for a predetermined time upon shifting from the temperature raising step to a standby mode, and then the control section stops supplying power to the heat source of the external heating member. 
   
   
     7. An image forming apparatus, comprising a fixing apparatus which includes: a fixing member which is rotatable; a pressure member for pressing the fixing member; and an external heating member for coming into contact with a surface of the fixing member so as to heat the surface from outside, a recording material being allowed to pass through a space between the fixing member and the pressure member so as to fix a toner image formed on the recording material,
 said fixing apparatus including a control section for controlling a state in which the fixing member is driven and for controlling a state in which power is supplied to heat sources respectively provided in the fixing member and the external heating member, wherein 
 the control section carries out a first fixing member maintenance process, in which the fixing member is kept rotating also after stopping supplying power to the heat source of the external heating member, when shifting from a temperature raising step for raising a surface temperature of the fixing member so that the surface temperature is equal to a preset fixing temperature to a standby mode so as to stop supplying power to the heat source of the external heating member, and 
 based on a surface temperature of the external heating member, the control section keeps the fixing member rotating during a period in which a surface temperature of the external heating member drops in a contact portion with respect to the fixing member so as to be equal to or lower than a durable temperature of the surface of the fixing member; and 
 the control section carries out a second fixing member maintenance process, in which time for beginning to supply power to the heat source of the external heating member is delayed from a time for beginning to supply power to the heat source of the fixing member, when carrying out a temperature raising step on start up or a temperature raising step upon restoration from a sleep mode; 
 wherein the control section begins to supply power to the heat source of the external heating member when the surface temperature of the fixing member attains a softening temperature of toner, in carrying out a temperature raising step on start up or a temperature raising step upon restoration from a second sleep mode in which the surface temperature of the fixing member rises from a temperature lower than the softening temperature of the toner, and after the toner softening temperature is reached both the heat source in the fixing member and the heat source in the external heating member are turned on until a fixing temperature is reached.